You can also trigger the quest by buying the house in windhelm. When you enter your new house... *SPOILER* turns out a murderer used it for his crimes. Explore for THREE CLUES *SPOILER* Two Journals and an Amulet, and make sure you SPEAK TO THE COURT WIZARD AT THE END INSTEAD OF TALKING TO THE STEWARD!

(***XBOX ONLY/Spoilers***) If you cannot start the quest chain, try this, it works for xbox users sometimes. Goto Tova Shield-Breakers house at night, and pick-pocket the key off of her, then go into the house, and pick up the 2 journals and the amulet. The Journals are in the bloody chest, and in a hidden room hidden behind a false door to one of the wardrobes. The amulet is hidden under some pamphlets on a shelf. Make sure to grab one. This should jump start the quest. Good luck.

---------------------------------------------------------------------------"Only the dead have seen the end of war." ~ Plato

I played with this quest using the MS11EnteringWindhelm variable (the quest apparently is partially triggered after the 4th time you enter Windhelm).

With a much newer character the didn't naturally get the quest triggered, I was able to travel back to Windhelm and manually set the variable back down to 3 and then enter Windhelm again and the quest triggered.

But with an old character (over 80 hours invested), I wasn't able to replicate this. No matter what I set the variable to or how I entered Windhelm, I couldn't get it to trigger.

So there's possibly another variable or something to do with the Radiant quest system at work here. What I mean is, with the way the Radiant quest system works, if you have certain quests in your journal, for some reason, they will prevent you from being able to get or trigger other quests. It wouldn't even be logically connected quests. Like a random bounty quest from Whiterun could prevent you from getting the quest to get a sword for Windhelm's blacksmith.